i'm adding to my original post something i came across in my research. i thought it might be helpful if anyone else is searching for this information, too... LINK to the article
Uterine Rupture in Pregnancy / Author: Gerard G Nahum, MD, FACOG, FACS; Chief Editor: David Chelmow, MD
it's an article that is a literature review from:
peer-reviewed literature was searched using the PubMed, Medline, and Cochrane databases for all relevant articles published in the English language. The search terms were uterine rupture, pregnancy and prior cesarean section, vaginal birth after cesarean, VBAC, trial of labor (TOL), trial of labor after cesarean (TOLAC) uterine scar dehiscence, and pregnancy and myomectomy. Standard reference tracing was also used.
Articles published from 1976-2010 that described the incidence of uterine rupture and that included sufficient information regarding the authors' definitions of uterine rupture and of uterine-scar dehiscence were incorporated for review. All studies were observational or reviews. A total of 109 published articles were included for data extraction and analysis.
here's the relevant info to this thread, though the whole article is pretty interesting.
Elkousy et al found that, in 9,960 women who underwent a TOL after 1 previous cesarean delivery, the risk of uterine rupture was significantly greater for fetuses that weighed >4000 g (2.8%) than in those weighing < 4000 g (1.2%; RR 2.3, P < .001). For women with 1 previous cesarean delivery and no previous vaginal deliveries, the uterine rupture rate was 3.6% for women with a fetal weight of >4000 g compared to women with a fetal weight of < 4000 g (RR 2.3, P < .001).
Zelop et al reported that the rate of uterine rupture for women delivering neonates weighing >4000 g was 1.6% versus 1% for newborns ≤4000 g, but that the difference was not statistically significant (P =0.24). More recently, Jastrow et al showed that birth weight was directly correlated with the rate of uterine rupture, with uterine rupture rates of 0.9%, 1.8%, and 2.6% for birth weights of < 3500 g, 3500-3999 g, and ≥4000 g, respectively (P < .05).